Despite the remarkable success in controlling former epidemics worldwide, vaccines effective against a number of serious infections, including those caused by pathogenic Escherichia coli (E. coli), Helicobacter pylori, and Staphylococcus aureus, remain largely unavailable.1, 2 Meanwhile, existing antibiotic regimens are increasingly threatened by the rapid emergence of bacterial drug resistance.3 Together, these challenges have motivated the search for novel antibacterial vaccine strategies.4-6 Among various reported approaches, integrating synthetic nanoparticles with cues from natural immunity has shown tremendous promise.7, 8 A plethora of nanoparticle-based vaccine systems have been developed to better manipulate immune responses and to potentially enhance antimicrobial immunity.9 
On the front of nanotechnology development, combining synthetic nanoparticles with natural cellular materials has led to the creation of various biomimetic nanoparticles.10, 11 In particular, using natural cellular membranes to cloak synthetic nanoparticles through a top-down fabrication method has recently attracted much attention.12 The resulting cell membrane-coated nanoparticles preserve the highly tunable physicochemical properties of synthetic nanomaterials while harnessing complex cellular functions that are otherwise difficult to replicate. Based upon this new strategy, a variety of nanoparticle platforms mimicking natural cellular functions have been developed, including red blood cell (RBC) membrane-cloaked nanoparticles with long-circulating properties,13 leukocyte membrane-coated silica microparticles capable of traversing endothelium,14 and cancer cell membrane-coated nanoparticles with inherited homotypic cell binding as well as tumor-specific immune activation.15 Cell membrane-coated nanoparticles have also enabled novel therapeutics beyond traditional practices. For example, by exploiting particle-bound RBC membranes, these biomimetic nanoparticles can function as a toxin nanosponge to absorb and neutralize a broad spectrum of pore-forming toxins regardless of the toxins' molecular structure.16, 17 These toxin-sequestered nanoparticles can further present the undisrupted toxins to the immune system as a safe and effective toxin vaccine.16, 17 